Synthetic plastic article and method of making the same



Aug. 14, 1945. J. F. MOTSON 2,382,806

SYNTHETIC PLASTIC ARTICLES AND METHOD OF MAKING THE SAME Filed Feb. 3, 1943 l" 0NTRL coN 6.-

an" 0N an 1 Q. CQNTRQL CON%-13 1L w 093/ up ,T a 1. 7 6 h) flitormey atentcd tag. it, 1945 STATES PATENT OFFICE SYNTHETIC PLASTIC ARTICLE AND METHOD OF MAKING THE SAME 4 Claims.

This invention relates to articles made from sheets of synthetic plastic materials and methods of making such articles and more particularly to the production of articles such as name or identification plates, instrument dials and the like. The invention further relates to the production of such articles having indicia with fluorescent characteristics.

In the prior production of articles made from synthetic plastic materials and having fluorescent indicia thereon the most common method heretofore used was the hand application of the fluorescent materials. Such materials were usually painted on by hand, and in some instances recesses of the shape desired to provide the required indicia were first formed in the material. Such methods were slow and cumbersome, frequently lacked uniformity, the indicia were not as distinct and sharp in outline as was desired, and there was the likelihood of errors in the application of the fluorescent material.

In the prior efforts looking to the production of synthetic plastic articles with fluorescent indicia thereon, also, attempts were made to use thin strips of fluorescent carrying material, these were secured to the plastic backing, the excess portions thereof were shielded with other thin strips and then heat and pressure were applied to hold the laminations in place. The result thus produced was not satisfactory because the indicia were not sharp and clear in outline, the character of the laminations frequently resulted in distortion and the laminations produced an uneven surface.

Attempts were also made to use stencils for applying the fluorescent material but the time required was excessive and the fluorescent portion of the resultant article lacked sharpness and clearness of outline.

It is the principal object of the present invention to provide improved methods of making articles of synthetic plastic materials with indicia thereon.

It is a further object of the present invention to provide improved methods of applying covering coatings or patterns to synthetic plastic sheet material.

It is a further object of the present invention to provide an improved indicia bearing article of synthetic plastic material.

It is a further object of the present invention to provide improved methods of applying indicia to synthetic plastic sheet material so that the indicia will have clear and sharp edges and uniformity of surface.

Other objects of the invention will be apparent from the annexed specification and claims.

The nature and characteristic features of the invention will be more readily understood from the following description, taken in connection with the accompanying drawing forming part hereof, in which:

Figure l is a perspective view of an article made in accordance with the present invention;

Fig. 2 is a view of a portion of a sheet of synthetic plastic material employed in connection with the present invention;

Fig. 3 is a sectional view taken on the line 3-3 of Fig. 2;

Fig. 4 is a view of a portion of a pattern or indicia sheet used in connection with the invention;

Fig. 5 is a view on a larger scale of a portion of the sheet of synthetic plastic material shown in Fig. 2 after treatment; and

Fig. 6 is a fragmentary sectional view on a still larger scale and taken approximately on the line 6-6 of Fig. 5.

It will of course be understood that the description and drawing herein are illustrative merely and that various modifications and changes can be made in the article and methods disclosed without departing from the spirit of the invention.

In the practice of the invention for obtaining an article Illa of the character shown in Fig. l a sheet ID of synthetic plastic material, such as that illustrated in Figs. 2 and 3, is preferably employed.

The synthetic plastic material in sheet form may consist of any desired type of synthetic plastic, such as phenolic resins, methyl methacrylate resins, urea resins, ethyl-cellulose resins, cellulose acetate resins, polystyrene resins, vinyl resins, and others. As illustrated in Figs. 2 and 3 the sheet is preferably laminated and consists of a lower or base lamination ll, an intermediate lamination I2, and an upper or face lamination 13. If desired the respective laminations ll, l2 and I3 may be of different plastic materials suitably secured together.

The lower or base lamination ll may be of any color such, for example, as the black color of certain of the phenolic resins. The upper or face lamination l3 preferably has incorporated therein a fluorescent or phosphorescent material selected in accordance with the light source utilized for illumination thereof, such as the ultra violet light radiations, and of the desired color required upon fluorescence or phosphoresence.

The upper or face lamination I 3 may also have any suitable coloring material incorporated therein, as desired, for its normal visual effect in natural light so long as the coloring material employed does not reduce the desired fiuorescing or phosphorescing effect. The intermediate lamination I! is preferably white in color to aid in obtaining the desired fluorescent or phosphorescent eifect in the face lamination. The thickness of the sheet l and of the lamination ll, l2, and I3 thereof is exaggerated in the drawing for purposes of explanation.

A pattern or indicia sheet H. as illustrated in Fig. 4, is prepared in the form of a positive transfer sheet. The pattern sheet carries the desired indicia I5, such as letters, characters and the like, upon thin transparent material. If desired suitable cut or separation lines l6 may be provided for indicating the lines of separation of the respective articles Ill. The indicia I are preferably impervious to light and may be black or otherwise opaque to prevent the transmission of light as hereinafter pointed out. The indicia it are preferably arranged in repeats vertically and horizontally as required so that a simultaneous transfer may be efiected, as hereinafter pointed out.

The sheet I0 is coated on the outer face of the upper lamination l 3 with 9, suitable adherent sensitizin agent and the coating permitted to dry. For this purpose materials of the character employed for sensitizing zinc and copper plates may be employed. One such material is available on the market under the name of "Cold Top and contains alcohol soluble varnish, ammonium bichromate, ammonia and shellac.

The indicia sheet I is superimposed on the light sensitized surface of the plastic sheet I!) and the same are then exposed to the action of light of high intensity, such as that from a double carbon arc. The exposure is for a very short interval of time, of the order of 8 to 18 seconds, 12 seconds being quite satisfactory. The portions of the sensitized surface which lie beneath the indicia l5 are protected from the action of the light by the opaque character of the indicia Hi. It has been found that if the interval of time is excessive unsatisfactory results will be produced. A simultaneous transfer of the repeats of the pattern sheet ll onto the plastic sheet In is thus initiated.

The exposed sheet I0 is then treated with a suitable developer to remove the portions of the sensitizing material not acted upon by the light, and for other purposes. The developer for the sensitizing material heretofore referred to preferably consists of an alcohol or water soluble opaque dye preferably carried in a suitable solvent. The coloring materials heretofore used in connection with the zinc and copper plate photoengraving processes have not proven satisfactory in practice with plastics. One suitable developer consists of approximately 2 ounces of nigrosine dissolved in approximately 1 pint of denatured alcohol (185-190 proof).

The developer removes the portions of the sensitized material which were covered and protected by the indicia 15 on the indicia sheet ll. At the same time the dye carried by the developer is absorber by and interspersed in the portions of the sensitized material which were exposed to the light. If the length of time of exposure is excessive the impregnation by and deposition of the dye will not take place to a satisfactory extent.

There is thus provided an opaque coating I1 which covers the entire surface of the sheet I 0 except for those portions which appear as the indicia 18, as illustrated in Figs. 1, 5 and 6.

The sheet I0 as shown in Fig. 5 may then be coated on the upper surface with a clear lacquer to prevent injury to the opaque coating l1, and separated by sawing, by punching or in other desired manner to provide the individual articles Ill.

The articles I ll as shown in Fig. 1 consists of a laminated synthetic plastic plate having an outer obscuring coating l1 which effectually covers the outer surface so that, with the exception of the indicia l8, the outer surface is not seen in either its normal or its fluorescent or phosphorescent condition. Th indicia I8 are available for normal visual observation or for observation in a fluorescent or phosphorescent condition and are clear and distinct in outline.

Under some circumstances the fluorescent or phosphorescent material carried in the upper lamination l3 may not be required and in this case the intermediate lamination l2 will also not be required. In all other respects the same steps will be followed for the production of the article. The color of the upper lamination l3 will be selected in accordance with the color of the obscuring coating l'l to obtain the desired contrast for visibility and pleasing effect.

I claim:

1. The method of making indicia bearing plates and the like of relatively rigid synthetic plastic material which consists in coating a fluorescent material carrying portion of synthetic plastic material with a light sensitive material, disposing a translucent indicia carrying sheet over said coated surface and exposing the exterior surface of the indicia carrying sheet to a light source, removing the unexposed sensitized material and simultaneously depositing an alcohol soluble shielding coloring material having the characteristic of shielding from normal visual and fluorescent visual observation on the portions of the surface exposed to the light source.

2. The method of making indicia bearing plates and the like of synthetic plastic material which consists in coating an ultra violet light responsive material carrying portion of synthetic plastic material with a light sensitive material, disposing a translucent indicia carrying sheet over said coated surface and exposing the exterior face of the indicia carrying sheet to a light source, removing the unexposed sensitized material, and simultaneously depositing at the light exposed locations a fluorescent shielding coloring material having the characteristic of shieldin from normal visual and ultra violet visual observation the portions of the surface exposed to the light source.

3. The method of making indicia bearing plates and the like of synthetic plastic material which consists in coating a surface portion of synthetic plastic material carrying an ultra violet light responsive material with a light sensitive material, disposing an indicia carrying sheet over said coated surface and exposing the exterior face of the indicia carrying sheet to a light source, removing the unexposed sensitized material and simultaneously depositing in the exposed sensitized material an alcohol soluble shielding coloring material having the characteristic of shielding from normal visual and ultra violet visual observation the portions of the plastic material surface exposed to the light source.

4. The method of making indicia bearing plates and the like of synthetic plastic material which consists in coating a fluorescent material carrying portion of synthetic plastic material with a light sensitive material, disposing a translucent inclicla carrying sheet over said coated surface and exposing the exterior face of the indicia carrying 5 sheet to a light source, removing the unexposed sensitized material with an alcohol containing 

